Using an on-chip DC-DC converter for promoting energy conservation has become common. In this case, a nonlinear control (e.g., hysteresis control) DC-DC converter, which is simple in circuit configuration, having a high response speed is often used.
However, in fields such as a wireless communication where strict requirements are imposed on noise, it is required to make an operating frequency of the DC-DC converter constant. However, since the nonlinear control scheme does not need external clocks, there is a problem in that the operating frequency of such a DC-DC converter is not constant.
To address the problem, it has been proposed that a PLL (Phase Locked Loop) be applied to the nonlinear control DC-DC converter; however, this increases the circuit size of the DC-DC converter due to addition of the PLL.